Gay fruit flies

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Ebru Demir and Barry Dickson have shown that splicing a single male gene into female drosophila causes them to generate male sexual behavior, including approaching females rather than males [*]:
fruitless Splicing Specifies Male Courtship Behavior in Drosophila
Ebru Demir and Barry J. Dickson*

All animals exhibit innate behaviors that are specified during their development. Drosophila melanogaster males (but not females) perform an elaborate and innate courtship ritual directed toward females (but not males). Male courtship requires products of the fruitless (fru) gene, which is spliced differently in males and females. We have generated alleles of fru that are constitutively spliced in either the male or the female mode. We show that male splicing is essential for male courtship behavior and sexual orientation. More importantly, male splicing is also sufficient to generate male behavior in otherwise normal females. These females direct their courtship toward other females (or males engineered to produce female pheromones). The splicing of a single neuronal gene thus specifies essentially all aspects of a complex innate behavior.

Makes you wonder about the implications for human behavior, doesn't it?

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9 Comments

So, what is a male gene in this context? In fact, in what
context exactly are we?

When we think of gene expression 'round this manor, squire, we think of biochemical interactions at what cell biologists like to call the "pretty tiny". Genes that cause certain proteins (in certain shapes) to be produced; multiple copies of those genes producing enough of a specific protein to affect the expression of other genes, and so on. These things can cascade, and you can get some interesting effects, but the longer the change of causality the harder it gets. W(a*10^23)y harder.


Getting from there to instictive behavior expression (like the tracking behavior of the eye in frogs) is hard, in other words, damn work. Getting from there to behavior in social animals,
she tends toward bad, bad science. Find me the gene that
causes men not to want to give up the remote, prove that changing it allows them to give it up and has no other side-effects, and then you get to play in the sexual playpen.


Metaphorically speaking, of course.

Well, in this case, what we're talking about, as indicated in the abstract, is that fru is spliced in a certain way in males and another in females. When you replicate the male pattern in females, you get the male sexual behavior. Other than that, I'm not sure what your point is... Yes, it's surprising that such a small tweak radically alters drosophila behavior. That's why I thought it was worth posting.

I think the point is that insect behaviors--even the very elaborate ones--tend to be remarkably directly hardwired, whereas comparable ones in higher animals are generally much less so. Think of (hardwired) bee dances vs. (partially learned) birdsongs, for instance--let alone human communication. Hence the fact that sexual orientation in fruit flies is controlled by a single gene is far from convincing evidence that it's similarly hardwired in higher animals.

I agree with Dan, but I would go further. Showing that changing a single neuronal gene causes flies which would not normally express a behavior to express that behavior seems to be what is described. The article doesn't use those words, though, it says: "is essential for male courtship behavior and sexual orientation".


The use of the last two words should be setting off large alarm bells, especially in the light of the text of the article itself (http://www.cell.com/content/article/fulltext uid=PIIS0092867405004071). It casts the discussion in terms of "switch" genes for the expression of phenotypic expression of things like, say, limbs, and says they went out looking for similar in terms of expression of instinctive behavior. They went looking in the sexual expression pool because:


"f behavioral switch genes exist, then one place in which they are likely to be found is in the specification of sexual behaviors (Baker et al., 2001). Males and females generally have dramatically distinct and innate sexual behaviors. These behaviors are essential for their reproductive success, and so strong selective pressure is likely to have favored the evolution of genes that “hardwire” them into the brain."


The Baker article is availabe at:
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WSN-42T4FS9-4&_coverDate=04%2F06%2F2001&_alid=283924927&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=7051&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=654d69caeaffaeb2f3032d9329090614.


Knowing it is playing with fire, the Baker article starts with a long description of what behavior is, what modifiable behaviors are, and why you don't want to confuse the two. It is, in other words, slightly more careful sociobiology than Demir and Dickson, and a lot more careful than a casually tossed "Makes you wonder about the implications for human behavior, doesn't it?"


It shouldn't make you wonder about the implications for
human behavior unless you also think human behaviors
like hogging the remote are innate. If you think that
and can demonstrate it, you are a winner. If you think
that and cannot demonstrate it, you are not. If you think
that, cannot demonstrate it, and act on it anyway,
you are the early 20th century eugenics nightmares and
"Exodus Ministries".


'Knowing it is playing with fire, the Baker article starts with a long description of what behavior is, what modifiable behaviors are, and why you don't want to confuse the two. It is, in other words, slightly more careful sociobiology than Demir and Dickson, and a lot more careful than a casually tossed "Makes you wonder about the implications for human behavior, doesn't it?"'

Yes, you'll note that there's also a difference between a journal article and a blog post.

That said, I don't find the argument you're making particularly persuasive. The interesting about this result isn't that the behavior is hardwired. That's not surprising at all, since, as you and Dan both argue, most of what insects do appears to be hardwired--though it's worth noting that much of human sexual response (primarily the immediate physical stuff like erections, vaginal lubrication, heart rate increase, etc.) is also hardwired. What's interesting is how easily retargeted it is. It would be easy to imagine a specification for fruit-fly behavior that was extremely difficult to retarget. And since retargeting is *precisely* what's at issue in the context of human sexual orientation, it seems to me that this is an interesting result. No, Dan, it's not dispositive, but interesting.

" it's worth noting that much of human sexual response (primarily the immediate physical stuff like erections, vaginal lubrication, heart rate increase, etc.) is also hardwired"


Dude, there are people who get these responses from trains. What the response is may be
hardwired, but what it is wired to has such a wide variability
that the parallel is weak. And I mean that as Cartman-weak.


As for the retargetting being so simple, wet-benching may
have hit the high schools, but simple it ain't, and the parallels
to what can happen during replication are harder to draw
than you'd think.


Finally, on the point that is not a peer-reviewed journal,
what do you think comment forms are for? Peer review,
n'est ce pas? And if you do this daily, an old word for
blog would be....


Skippy, you're acting as if Eric asserted you could retarget sexual behavior in humans through such a technique.

Clearly, this isn't the case. As he points out, this result is interesting for behaviors in general. I think the most you can say about what he implied, is that if we did identify a hardwired behavior in humans, we might be able to retarget it easier than you think.

Personally, my first thought was about treating OCD rather than altering human sexuality.

Actually, I'm not suggesting that we can retarget it at all--nor that we'd want to.

Rather, I'm suggesting that it provides weak support for the hypothesis that the variation in human sexual response is at least partly genetic. I suspect you misunderstand what I mean by simple--not that we could do it easily in the lab but rather that it's suggestive that it's a state that's accessible by natural variation.

I guess what bothers me about the inference is that this recent discovery wasn't really necessary for it. Pretty much everything a fruit fly does is genetically wired, so simply observing that male (but not female) fruit flies do a particular little dance for female (but not male) fruit flies is pretty much enough to infer that there's the behavior is genetically determined. Whether there's a particular gene that turns it on and off doesn't strike me as that relevant--it could have been three separate genes, or some more complicated pathway, but regardless, the behavior was bound to be genetically programmed.

Again, what this says about human behavior, with its many layers of environmental, developmental and cognitive influences on top of its genetic blueprint, seems really hard to figure out with any confidence.

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